Framework support systems that are articulated by a hinge or like pivotal support structure for pivoting a section of the framework between two alternate in-use positions, and that are spring-biased so as to be stable in either position, are found in a myriad of applications too numerous to enumerate.
One of such applications to which the present invention is directed involves problems encountered with helmsman operation of power boats or similar water-borne pleasure craft due to the close orientation of the steering wheel and helmsman seat in the helmsman station of the power boat. The seat bottom construction of the helmsman chair is designed to comfortably support the helmsman in seating position with his knees beneath the steering wheel so that the helmsman can comfortably manually grip the steering wheel for guiding the power boat. This requires that the front edge of the seat bottom be located at a lower elevation and only slightly aft of the closest portion of the steering wheel. Hence there is little or no clearance between the steering wheel and the front edge of the seat bottom to allow the helmsman to comfortably stand up and steer the boat with the steering wheel centered in front of him. However, as is often the case when docking, the helmsman needs to quickly standup for better visibility all around the boat, and particularly over the bow. With one-section seat bottoms of fixed construction he cannot do this easily because typically the seat bottom of the helmsman chair is in his way.
In an effort to overcome this problem a helmsman seat bottom construction recently has been provided that is constructed in two sections, a fixed immobile rear section and a movable front section hinged to the main framework of the chair so as to be normally supported in a horizontal position as a horizontal forward extension of the seat bottom rear section. When the aforementioned docking situation arises and the helmsman needs to standup, the front section may be manually pivoted upwardly and rearwardly so as to be disposed over the rear section, thereby providing the needed increase in standing room clearance between the steering wheel and seat bottom.
However this prior swinging front section was stabilized only by gravitational forces in both up and down positions. Although this manner of pivot stabilization is satisfactory for the horizontal position of the front section when the helmsman is sitting on the chair, due to the typical rocking and pitching motion encountered in power boat operation the front section was found to be not satisfactorily stabilized by gravitational forces in the up position, even when the up position was set by stops slightly over-center in the aft direction.
The use of hook and eye type catches or the like is not a satisfactory solution to this stabilization problem since hooking such a catch diverts the attention of the elmsman from control of the power craft precisely at the time when all his attention is most needed for maneuvering. Likewise, although power boat seats are often mounted for fore and aft adjustment on sliding rail constructions, the mechanism for locking the chair in place in adjusted position is not adapted to enable quick, automatic push back of the chair seat to provide the needed standing room clearance.